Doc Rivers saw it. Paul Pierce knew it.

The Celtics captain was sulking in the third quarter as the Warriors came out fast and took the lead after Boston controlled most of the first half.

Both knew it had to change and fast.

“Yeah, I think I was the one that kind of brought the body tone down a little bit, because I made some bad turnovers there to start the third quarter, kind of got me down,” Pierce said. “So it was up to me to kind of get it back, get the team back on. That’s what I try to do, I cant have any lapses like that because it really affect the team and I realize that, so I have to do a better job in that department.”

“He started out playing great and then when I subbed him and brought him back in, I don’t know what happened. We were turning the ball over and he was struggling,” Rivers said. “It was funny, in the third quater, the only thing I told him was I don’t care that you’re not playing well in this stretch or we’re not, I just hate our body language right now. And I give Paul a lot of credit, he basically said, ‘That’s on me. That’s my fault.’

“I thought we were hanging our heads a lot in the third quarter. We were turning the ball over and we were missing shots. The end of the world is not going to happen. We just have to keep playing. I didn’t like the way we responded to that and I thought Paul did a good job in the timeout right after that of getting the guys back.”

Pierce finished with a game-high 26 points in Boston’s 94-86 win over Stephen Curry and the Warriors Friday night at TD Garden.

“It was good,” Pierce said. “You play a quality ball club who’s playoff-bound who’s very dangerous in the West, capable of beating anybody. Sometimes that first game at home feels like a road game, your body is readjusting. You know you haven’t been in this building in a couple of weeks, so sometimes its difficult. We were a little sloppy with the ball, but it’s a good win nevertheless.”

The Celtics actually went into a zone defense when Avery Bradley went out with his fifth foul with eight minutes left in the third quarter.

“I think it really bothered them,” Pierce said. “They’re a great one-on-one team who really thrives on taking you off the dribble, making an extra pass, shooting the three-ball….I think it altered their offense a little bit once we got into the zone. It was really effective, especially in the second half.”

Jeff Green took a hard spill on his left side midway through the third and when he returned, the Celtics went on a 9-0 run to pull away for good late in the third.

“He was awesome tonight,” Pierce said of Green, who finished with 18 points. “He really carried us in that fourth quarter, took it upon himself to be aggressive. You know, he’s coming into his own, after a slow start, which you can expect. Its tough when you take a year off from basketball and try to get back in the game, but I think since January he’s just been phenomenal, very consistent doing what we ask on both ends of the court, and he’s getting better and better as time goes on.”